It has long been recognised that neurological deterioration in trauma victims is dramatically reduced when a hypothermic state is induced. This phenomenon has been observed, for example, when an accident victim has fallen into cold, icy water resulting in hypothermia. A similar phenomenon was observed during the Napoleonic Wars, when wounded soldiers who were left “out in the cold” managed to survive their injuries, whilst their counterparts who had been warmed by a nearby fire perished. More recently, medical practitioners have made use of this phenomenon by deliberately inducing mild hypothermia in patients, prior to emergency treatment or during surgical operations. This causes the body's vital functions to be slowed down, thus reducing the chances of brain damage occurring in the patient. In extreme circumstances, the patient's core temperature can be reduced by submerging the patient in a bath of ice water, or by pumping cold fluids through or next to their internal organs. Cooling has also been noted to be particularly effective when applied directly to the patient's head.
The human skull has many small holes passing through it, known as emissary foramina, through which veins transport (hot) blood from the scalp into the venous sinuses. The blood transported to the surface of the head is cooled by the surrounding environment and by sweat evaporating from the surface of the skin, before re-entering the skull at a lower temperature, to help keep the brain cool. This explains how cooling the head at the surface can produce significant cooling within the human brain, even at significant depths within the skull, more quickly than would be expected to be achieved through mere thermal conduction.
Cranial cooling has been noted to reduce brain damage and increase survival rates in accident victims, and patients with head injuries are often treated in accident and emergency departments by cooling the patient's head. It is, however, often the case that a victim will have suffered their injuries significantly in advance of their arrival at a hospital “Accident and Emergency” department. If the delay between receiving an injury and receiving treatment at a hospital or other medical care facility is too long, significant neurological deterioration may already have occurred in the interim, and brain damage may thereafter be unavoidable. The sooner that effective brain cooling can be applied to victims of serious injury, the more effective the cooling will be to prevent the onset of brain damage. The crews of emergency response vehicles are often the first on site with any means for treating a victim of severe injuries, but as yet paramedic teams do not widely carry head-cooling apparatus as part of their standard equipment, if at all. What is required is an easily portable means of equipment by which paramedics and other emergency medical practitioners can easily and effectively apply head cooling to victims of serious injury in danger of suffering neurological deterioration as a result of their injuries sustained. One proposed solution is a nasal spray device, which administers a fine mist of PFCs (perfluorochemicals) into a patient's nasal cavity. The mist droplets evaporate on contact with the back of the nose to absorb heat and carry it away from the nose, which in turn cools the brain.
One particular group of injured patients liable to have sustained head injuries are motorcycle accident victims. Due to the exposed and unrestrained position of a motorcycle rider on their vehicle, motorcyclists who are involved in accidents often sustain severe injuries. By far the most common cause of fatalities amongst motorcycle accident victims, however, are head injuries resulting in brain trauma. Since as far back as 1946, it has been recognised that wearing a motorcycle safety helmet significantly reduces the chances of a motorcycle crash victim suffering a fatal injury. It is now recommended, if not a requirement of law, in almost all developed countries, to wear a motorcycle safety helmet when riding a motorcycle, and various safety standards have been set out which define the minimum performance requirements that a safety helmet must achieve in order to qualify for sale under the appropriate standards in the relevant territories.
A typical motorcycle safety helmet design is shown in FIGS. 1 to 3 of the present application. FIG. 1 shows a full-face motorcycle safety helmet (that is, a helmet which substantially fully encloses the wearer's head and face and extends around the region in front of the wearer's mouth and chin). The motorcycle helmet 1 includes the helmet main body 3, which has an opening 3a through which the rider can see, and a visor 5, which is selectively raisable and lowerable either to expose the rider's face, or to enclose the rider's face so as to deflect wind and debris.
FIG. 2 shows a cross-sectional diagram through the motorcycle helmet main body 3, indicating the typical main constructional elements thereof. The helmet main body 3 forms a layered shell which encloses a rider's head when worn. The main body 3 comprises a relatively thin rigid outer shell 10, a relatively thick layer of impact absorbing material 20 and an inner comfort layer 30. The function of the various layers is explained with respect to FIG. 3.
FIG. 3 shows diagrammatically how forces are distributed and absorbed by the various layers of the helmet during an impact. The rigid outer shell 10 deflects and distributes impact forces away from the impact point, laterally through the outer shell 10, as shown by the arrows labelled L. This dissipates the impact forces away from the point of impact, so that they are not concentrated at one point, preventing the safety helmet from splitting apart or being penetrated by the impacting object. The rigid outer shell 10 furthermore absorbs impact energy by an appropriate failure mechanism, such as splitting (cracking) or delaminating of the rigid outer shell material. The impact absorbing material layer 20 absorbs impact energy by deforming in the direction of the impact force, as shown by the arrows labelled I. The primary goal of the impact absorbing material 20, however, is to slow down movement of the wearer's head, by cushioning the forces on the wearer's head as the helmet is subjected to the impact force.
This reduces the magnitude of the force and acceleration which the brain undergoes as the impact takes place. A typical impact taking place during a motorcycle traffic accident might be the rider's head striking the concrete kerb at the side of a road. As the helmet strikes the kerb, it is brought relatively instantaneously to a halt. If the same deceleration were to be applied to the rider's head, the motorcyclist's more rigid skull would tend also to be brought promptly to a halt, whilst the softer brain matter, which has nothing holding it place, tends to continue travelling, leading to traumatic internal brain injuries. The impact absorbing material layer 20 serves as a cushioning member, giving the rider's head space and time in which to come to a halt under a more progressive deceleration, and thus hopefully avoiding serious brain injuries. The inner comfort layer 30 is provided between the impact absorbing material 20 and a user's head, to provide a comfortable tactile surface against the wearer's head when worn, and to provide softer localised padding so that the helmet will fit tightly and comfortably in place during normal use. The inner comfort layer 30 typically provides an air gap or channel to allow for ventilation around the wearer's head, and may take the form of a removable washable liner.
Motorcycle helmet design necessarily represents a trade-off between the level of safety and protection which the helmet can provide in an impact and the practicality with which the helmet can be worn when riding a motorcycle. Theoretically, the impact absorbing material 20 could be provided as a very thick construction, in one or more layers of varying degrees of density, so as to provide extensive progressive cushioning to the wearer's head during an impact. On the other hand, the helmet has to be of an overall size and shape that the motorcycle rider can wear it without undue interference from wind resistance and wind noise, and it must not be too heavy. Motorcycle helmet design has increasingly been driven towards smaller, more lightweight design, as newer materials have enabled existing safety standards to be met and surpassed with progressively more compact and lightweight configurations.
Nevertheless, despite advances in motorcycle safety helmet design, victims of motorcycle traffic accidents who wear such motorcycle safety helmets still sustain head injuries which result in brain damage. One problem in this regard is that even with rapid response times, a paramedic or other emergency medical practitioner often cannot be on the scene of the accident until some significant time after the accident has taken place. During this delay, neurological deterioration can occur, for example through bleeding into the brain, deprivation of oxygen supply, etc. The normal advice given to non-medically trained people attending motorcycle accidents is never to remove the helmet of the injured motorcycle rider, in case they may have sustained any damage to their neck or spine. During the ensuing time period, the motorcycle safety helmet tends to keep the motorcyclist's head insulated from ambient temperatures, and thus at a relatively high temperature (especially since there is no air flow through the helmet whilst the helmet is stationary). If the injured motorcyclist has sustained a head injury, this can lead to inflammation and swelling of the brain, within the skull and helmet. Often, the head can swell up inside the motorcycle safety helmet, making it difficult or impossible to remove the helmet, after a certain period of time has elapsed (the helmet can then not be removed until the injured motorcyclist arrives at a hospital, where specialist cutting tools, such as those normally used for removing plaster casts, can be used to cut the helmet away from the motorcyclist's head). These conditions can promote neurological deterioration, before any significant medical attention can be administered.
It would therefore be desirable to provide means by which the onset of brain damage can be inhibited in a motorcycle accident victim.
United States patent publication U.S. Pat. No. 5,950,234 A1, to Leong et al, discloses a cooling pack head covering. The cooling pack is intended to be worn so as to cover the scalp of a patient undergoing chemotherapy treatment. It is contemplated that the cooling pack may be a chemical cold pack, in which chemicals in a container become cold when they are mixed together by breaking a barrier which otherwise separates them. The cooling pack is generally circular and has a “V” shaped notch formed therein to enable the pack to be wrapped around and secured to a patient's head, in a generally bowl shape. It is contemplated that, if an American football helmet were to be used, then the cooling pack might be formed in multiple parts to fit in the helmet, with the objective of cooling the wearer's scalp to a temperature which will minimise hair loss. The cooling pack must be activated before being put on, and has no means by which to activate the cooling pack whilst being worn.
Further United States patent publication U.S. Pat. No. 5,469,579 A1, to Tremblay et al, discloses a head cooling device for mounting over a person's head, generally within headgear or a safety helmet, such as the construction hats worn on building sites. The head cooling device is configured to sit within the hat or helmet of a wearer, and to contain ice cubes therein. As the ice cubes melt, the head cooling device allows the melting water to pass one drop at a time onto the wearer's scalp, so as to absorb and extract heat from the wearer's head.
US patent publication U.S. Pat. No. 5,755,756 A1, to Freedman, Jr. et al, discloses a hypothermia-inducing resuscitation unit which includes a helmet adapted to be mounted on the head of a patient. A coolant source is pumped from external of the helmet into a bladder which is inflatable to achieve a tight fit over the head of a patient, and to provide cooling to the patient's head.